Today, there are several ways of downloading navigation map data for off board clients. The clients usually communicate with a server in order to fetch maps, calculate routes and perform searching.
One way is to use a tile based map system and download the map tiles, as they are needed during navigation as the GPS position is updated. The speed reported by the GPS will be used to select zoom level of the map for the route.
Another common way is to download maps that are custom made for the current route. This means that they are clipped to only contain roads and other geographical features that are in the near vicinity of the actual route.
Although a number of systems for downloading navigation map data have been introduced on the market, the data traffic consumption during download may be improved. Moreover, determining the zoom level from the speed of the GPS will lead to that several levels of possible map details will be downloaded for the same area in case the user stops at a traffic light or similar, which may lead to jerky zooming if the speed varies.